1. Field of the Invention
The present invention relates in general to automotive seats, and more particularly to automotive seats of a type which comprises a frame, springs supported by the frame and a cushion pad mounted on the springs.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional automotive seat of the above-mentioned type will be described with reference to FIGS. 4 and 5 of the accompanying drawings.
In the drawings, denoted by numeral 1 is a seat frame which is rectangular in shape. The frame illustrated comprises front and rear pipes (no numerals) and an apertured rectangular panel (no numeral) welded to the pipes at front and rear portions thereof. The rectangular panel has at its rear frame portion 1a a plurality of hooks 2 and and at its front frame portion 1b a plurality of holders 3. These hooks 2 and holders 3 are used for spanning a plurality of parallel S-springs 4 between the rear and front frame portions 1a and 1b of the frame 1.
As is seen from the drawings, each holder 3 is provided by a raised part of the panel, which comprises two semicylindrical tunnel portions and a somewhat depressed roof portion 3cinterposed between and integral with the tunnel portions.
As will be described hereinafter, before fixing the S-springs 4 to the frame 1, each holder 3 takes a simple configuration including a single but widened tunnel portion which is defined between two slits 3a and 3b. That is, each holder 3 is originally provided by forming the two laterally extending slits 3a and 3b in the left frame portion 1b and raising the middle portion 3cdefined between the slits 3a and 3b.
Each hook 2 is a generally U-shaped plate, which is secured at one wing to the rear frame portion 1ahaving the turned head portion 2b directed toward the front frame portion 1b, as is seen from FIG. 4. Designated by numeral 2a is an open portion defined between the other wing of the hook 2 and an upper surface of the rear frame portion 1a of the frame 1.
Between the holders 3 and the corresponding hooks 2, there are spanned the parallel S-springs 4. Each spring 4 has terminal end portions 4a and 4b, each extending in a direction perpendicular to the axis in which the spring 4 is extensible.
In order to mount the S-springs 4 to the frame 1, the following steps have been employed.
First, one terminal end portion 4a of each spring 4 is led into the turned head portion 2b of the corresponding hook 2 through the open portion 2a to achieve a hooked engagement with the hook 2. Then, stretching the spring 4, the other terminal end portion 4b of the spring 4 and it's neighbouring portion 4b' of the same, which thus constitute a generally U-shaped end portion of the spring 4, are thrusted into the single tunnel portion of the corresponding holder 3 from one open end to such a degree that the rounded head of the U-shaped end portion of the spring is exposed to the outside through the other open end. Then, the roof portion of the single tunnel is depressed, by a press machine, to constitute the aforementioned two semicylindrical tunnel portions through which the other terminal end portion 4b of the spring 4 and the neighbouring portion 4b' of the same are passed.
As is seen from FIG. 4, because the roof portion 3c of each holder 3 is depressed to narrow the middle portions of the open ends of the holder 3, disengagement of the U-shaped end portion of the spring 4 from the holder 3 is suppressed.
However, due to its inherent construction, the above-mentioned conventional seat has the following drawbacks.
First, because each holder 3 has the above-mentioned construction, dislocation of the U-shaped end portion of the spring 4 relative to the holder 3 tends to occur particularly at the time when the roof portion of the holder 3 is being depressed. Such displacement may also occur when the seat is subjected to a severe vibration. As is seen from FIG. 4, once such displacement occurs, parallel arrangement of the S-springs 4 on the frame 1 is broken and thus in this case, even supporting of the cushion pad by the springs 4 is not obtained. In fact, the holder 3 employed in the conventional seat has no stopper means for suppressing the displacement of the U-shaped end portion in the direction of the axis of the front frame portion 1b.
Second, when an abnormally large stress is suddenly applied to the middle portions of the springs 4, deformation of the front frame portion lb tends to occur. In fact, such a large stress is generated when a mischievous boy jumps up and down on the seat.